Re: I-D Action: draft-ietf-httpbis-incremental-02.txt

I have attempted to implemented Incremental and have some questions:

The Incremental header with value ?1 indicates that the messages
should not be buffered.  Draft Section 4.1 Permanent Rejection states:

   When an intermediary rejects an incremental message -- either a
   request or a response -- due to security concerns with regard to the
   payload that the message might convey, the intermediary SHOULD
   respond with a 501 (Not Implemented) error with an
   incremental_refused Proxy-Status response header field (Section 5).

RFC 9209 The Proxy-Status HTTP Response Header Field
https://www.rfc-editor.org/rfc/rfc9209
explicitly states in Section 2. The Proxy-Status HTTP Field:

    Origin servers MUST NOT generate the Proxy-Status field.

? How should origin servers reject Incremental?  HTTP origin servers
might be gateways to other protocols, such as CGI, FastCGI, SCGI, AJP13.
How should the origin server respond if the origin server/gateway is not
a reverse HTTP proxy?  Send HTTP status 501 but omit Proxy-Status?

? Related, for reverse HTTP proxy, if adding Proxy-Status but the server
has not defined a name for itself (ExampleCDN), or does not wish to
share its name, is there an acceptable token to use to indicate this?
  e.g. Proxy-Status: unspecified;error=incremental_refused
"unspecified"?  "anonymous"?  "private"?
Should I use the same token as the HTTP 'Server' response header?


If Incremental is not a valid structured-field boolean, then it
must be ignored.

   Only Boolean values (Section 3.3.6
   of [STRUCTURED-FIELDS]) are valid; a recipient ignores the field if
   it contains any other type.

? Should the header still be forwarded?  A strict
intermediary might choose to omit the header.  Is that permitted?
How might doing so affect header signatures?  Should Incremental
be excluded from header signatures?


? Should Incremental be added with HTTP/1.1 Upgrade response header?
(Or should the draft suggest to omit Incremental with Upgrade?)


? Should Incremental be ignored in *response* headers with status 1xx?
(There is no response body with HTTP status 1xx.)
Should the draft suggest omitting Incremental with HTTP status 1xx?


Cheers, Glenn

Received on Monday, 27 October 2025 09:14:12 UTC